Method of packing heat pipes within a pipe pile involving the optimized vibration of the packing material

ABSTRACT

A pair of heat pipes are placed within the interior of a pipe pile which has been grouted within an earth borehole. A predetermined amount of water is metered into the bottom of the interior of the pipe pile and then dry sand is added to the water. Various means are disclosed for vibrating the sand and water mixture including the vibration of the heat pipes and/or the vibration of the pipe pile. To maximize the amplitude of vibration, the frequency of vibration is varied during the packing process to match the unpacked length of the heat pipes, either by continuously varying the frequency of vibration or in steps along the length of the heat pipes.

United States Patent Wyant [451 Aug. 12, 1975 Primary Examiner-Jacob Shapiro Attorney, Agent, or FirmWilliam E. Johnson, Jr.

[75] Inventor: Reece E. Wyant, Houston, Tex f 57 ABSTRACT [73] Assignee: Dresser Industries, Inc., Dallas, Tex. 1

[22] Filed: Aug. 9, 1974 A pair of heat pipes are placed within the interior of a pipe pile which has been grouted within an earth bore- [211 App! 496321 hole. A predetermined amount of water is metered into the bottom of the interior of the pipe pile and [52] U.S. Cl 6l/53.52; 61/36 then ry Sand is added 120 the Water. Various means [51] Int. Cl E02d 5/00; E02d 3/02 r i losed f r vibrating the sand and water mixture [58] Fi ld of Sear h 61/5352, 36, 35, 50, 53, including the vibration of the heat pipes and/or the vi- 61/53.64, 53.66, 56, 56.5, 46; 264/31, 32, 33 bration of the pipe pile. To maximize the amplitude of vibration, the frequency of vibration is varied during [56] R f ren e Cit d the packing process to match the unpacked length of UNlTED STATES PATENTS the heat pipes, either by continuously varying the fre- 1 865 652 7/1932 Upson 61/53.64 of vibration or in steps alqng the length of the 3,706,204 12/1972 Long I. 61/46 heat plpes' FOREIGN PATENTS OR APPLICATIONS 7 Claims, 4 Drawing Figures 706,239 3/1954 United Kingdom 6l/53.52

28 23 Q 29 I g MONITOR I 20 VARIABLE 2| FREQUENCY V I B RATO R WA T E R SAN D W gym /r/ 1 X g 5 -15. 7 A a Q I 22 44 4 6 SHEET PATENTED W 21975 SHEET FIG. 4

l W M FIG. 3

METHOD OF PACKING HEAT PIPES WITHIN A PIPE PILE INVOLVING THE OPTIMIZED VIBRATION OF THE PACKING MATERIAL RELATED APPLICATION This application relates to my copending U.S. Pat. application Ser. No. 455,69l, for METHOD OF GROUTING A PILE IN A HOLE INVOLVING THE OPTIMIZED VIBRATION OF THE GROUTING MA- TERIAL, filed on Mar. 28, 1974.

BACKGROUND OF THE INVENTION This invention relates generally to the packing of one or more heat pipes within the interior of a pipe pile, and particularly relates to the packing of such heat pipes within the interior of a pipe pile while vibrating the packing material at an optimized frequency.

As described in the aforementioned related United States patent application, it has been proposed to build various pipelines across Alaska which will have piles grouted in place within earth boreholes using a mixture of sand and water in the annulus external to the pipe pile. It has also been proposed that a sand and water mixture be used to pack the heat pipes within the interior of the pipe pile to provide heat pipe stabilization of the pipe pile. This general area has been discussed in US. Pat. No. 3,788,389 for PERMAFROST STRUCTURAL SUPPORT WITH HEAT PIPE STA- BILIZATION" which issued on Jan. 29, 1974. It should be appreciated, moreover, that much of the construction work on these pipelines will be done under extremely frigid temperature conditions, for example, 60 F. These extreme conditions create problems with icing of the water being used and bridging within the interior of the pipe pile when pouring a sand and water mixture therein. Furthermore, it has been discovered that even while vibrating the mixture, the mixture will sometimes not be compacted around the heat pipe to such a degree as to create a satisfactory packing of the heat pipe within the interior of the pipe pile. In addition, while adding the sand to the water, the packing material is thus compacted along the length of the heat pipe, thereby shortening the unpacked length of the heat pipe. This causes the frequency of vibration to be out of tune with respect to that portion of the heat pipe being vibrated.

It is therefore the primary object of the present invention to provide a new and improved method of packing a heat pipe within the interior of a pipe pile;

It is also an object of the invention to provide a new and improved method of packing one or more heat pipes within the interior of a pipe pile which eliminates many of the problems encountered while using water is subfreezing temperature conditions; and

It is yet another object of the present invention to provide new and improved methods for vibrating the packing material used in packing a heat pipe within the interior of a pipe pile by optimizing the frequency of vibration one or more times during the packing process.

The objects of the invention are accomplished, in general, by a method of packing one or more heat pipes within the interior of a pipe pile which involves the placement of such heat pipes within the interior of the pipe pile, the addition of water to such interior and then the addition of sand to the interior and the vibration of the packing material at frequencies which are optimized for purposes of having greater amplitudes of vibration.

These and other objects, features and advantages of the present invention will be more readily understood from a reading of the following detailed specification and drawing, in which:

FIG. 1 is an elevated view, partly in cross section, of a pipe pile which has been grouted within an earth borehole in accordance with the methods disclosed in my aforementioned United States patent application;

FIG. 2 is an elevated view, partly in cross section, which illustrates apparatus for vibrating the heat pipes and for adding water and sand to the interior of the pipe pile in accordance with the present invention;

FIG. 3 is a diagram illustrating the reinforcement of the vibrational wave in accordance with the present invention; and

FIG. 4 illustrates, in elevation and partly in cross section, the heat pipes which have been packed within the interior of the pipe pile in accordance with the methods of the present invention.

Referring now to the drawing in more detail, especially to FIG. I, there is illustrated a hole 10 in the earth 11 which may be either a conventional earth formation, or may be comprised of permafrost in the more frigid zones of the earth, for example, in Alaska. A steel pile 12 is grouted within the hole 10 in accordance with the principles of my aforementioned related United States patent application. The pipe pile 12 is grouted within the hole 10 by a compacted sand and water mixture 13. As is explained in the aforementioned related application, the pipe pile 12 may or may not have a bottom end plug at its lower extremity.

Referring now to FIG. 2, a pair of heat pipes 20 and 21 separated by one or more separators 22 along their length are placed within the interior of the pipe pile 12. It should be appreciated that the heat pipes themselves are conventional and may take several forms, for example, as illustrated and described in US. Pat. No. 3,788,389. Alternatively, heat pipes such as Model l333I-I available from the Hughes Electron Dynamics Division, 3100 West L/omita Blvd., Torrance, Calif. 90509 can be used. A variable frequency vibrator 23 is attached to the top portion of the heat pipes 20 and 21 to vibrate such heat pipes along their length. The variable frequency vibrator can be of any conventional design, for example, an air-actuated L-3 piston-type vibrator available from the National Air Vibrator Company of 6807 Wynnwood Lane, Houston, Tex. A source of water 24 and a source of sand 25 are provided for placing water and sand into the interior of the pipe pile 12. A monitor 28 is attached by a conductor 29 to the vibrator element, or alternatively, to the heat pipes 20 or 21 to monitor the amplitude of vibration. The monitor 28 is conventional, for example, an oscilloscope, using conventional amplitude detecting techniques. It should be appreciated that the invention also contemplates the packing operator adjusting the vibration frequency based upon either audible or visible indications of the maximizing of the vibration amplitude. One such successful optimizing of the frequency was accomplished by having the packing operator feel the movement of the top of the heat pipe while varying the frequency of vibration. Another successful operation was accomplished by observing the maximum agitation of the downhole water surface within the interior of the pipe pile at the optimum frequency.

In practicing the method in accordance with the apparatus illustrated in FIG. 2, the heat pipes 20 and 21 are placed inside the interior of the pipe piie l2 and water 26 is then metered into the interior of the pipe pile 12 from the water source 24 in a predetermined amount which is determined by the area of the interior of the pipe pile along the entire length of the pipe pile l2 and by the amount of water as is desired in the final sand and water mixture. By way of example, a recommended packing mixture should have a water content of 8 to 15% by dry weight. The 15% water content has been found to be highly desirable in that the mixture is highly fluidized during at least a portion of the method according to the present invention.

After the water 26 is added to the interior of the pipe pile 12 and is residing in the bottom of the pipe pile, the dry sand is added to the interior of the pipe pile 12 from the sand source 25 and the vibrator 23 is used to vibrate the heat pipes and 21 which in turn causes the sand and water mixture to vibrate. Because of the important feature of adding the water to the interior of the pipe pile first, no air bubbles are found within the sand and water mixture as would be the case if either the sand was added first or if the sand and water slurry was mixed prior to adding the mixture to the interior of the pipe pile. By placing the water in the interior first, and by vibrating the sand and water mixture, it has been found that there is an excellent adherence of the sand and water mixture to the interior of the pipe pile and to the heat pipes themselves. As will be explained hereinafter with regard to FIG. 3, the frequency of the variable frequency vibrator 23 is varied one or more times during the packing process to optimize the frequency of vibration.

Referring now to FIG. 3, there is diagrammatically illustrated a pipe pile 120 in place within an earth borehole 121 which has been grouted by a compacted sand and water mixture 122 in accordance with the principles of my aforementioned United States patent application. Heat pipes 123 and 124 have been placed within the interior of the pipe pile 120 and a portion of the sand and water within the interior of the pipe pile 120 has been compacted as area 125. in addition to the compacted sand and water mixture 125, free-standing water 126 is also present within the interior of the pipe pile 120. As the heat pipes 123 and 124 are vibrated at any given frequency, the waveform, for example, the waveform diagrammatically illustrated and identified by the numberal 127, is clamped or nulled out at the point 128 which coincides with the point of compaction along the heat pipes 123 and 124. Because of the compaction at the point 128, the heat pipes are substantially unable to vibrate at that point. Depending upon the frequency of vibration, the waveform 127 may or may not be tuned to the unpacked length of the heat pipes, i.e., the length of the heat pipes 123 and 124 between the point 128 and the uppermost end of the heat pipes 123 and 124. In the particular waveform 127 which is illustrated, being the worst case situation, the

waveform 127 reaches a null point coinciding with the' vtop end of the heat pipes 123 and 124 and thus would have a very low amplitude and be quite inefficient. By varying the frequency of vibration, and thus producing the waveform as illustrated by the waveform 129, the waveform is nonetheless clamped at the point 128 but is seen to have a maximum amplitude at the point 130. Thus, the amplitude of vibration is maximized.

As previously explained, the invention contemplates that the optimized frequency is readily ascertained by various observations, for example, by watching for a maximum agitation of the surface of the standing water 126, by monitoring the amplitude of the vibration of the heat pipes 123 and 124, by listening for maximum amplitude of vibration or by various other ways to indi cate that the vibration has been tuned to the unpacked length of the heat pipes 123 and 124.

In understanding the process according to the present invention, it should be appreciated that the heat pipes have a natural frequency of vibration which depend on their free length above the point where the packing material constrains the vibration. As the level of the packing material rises within the interior of the pipe pile, the free length decreases and its natural frequency increases, much as the pitch of a violin string rises as the violinists fingers shorten the vibrating strings length. If a vibrating force is applied to the heat pipes at their natural frequency, then the input vibrations reinforce the heat pipes vibrations and the maximum vibration amplitude is attained. If the applied vibrating force is not a reinforcement frequency, an interference will be produced and the heat pipes will not vibrate as much. Thus, as the heat pipes free length changes, the vibrators frequency should be changed to obtain the maximum vibration of the heat pipes during the entire process. The maximum vibration transfers the greatest energy to the packing mixture giving the most effective packing. It is not necessary, however, that the vibrator have the exact same frequency as the natural vibration frequency of the heat pipes. If the vibrator applies force impulses at some frequency so that the vibrators impulses will reinforce the vibration of the heat pipes, the vibration amplitude will be increased and the desired results are achieved.

In practicing the invention, it is contemplated that the vibrator may be continuously varied as the compaction occurs above the length of the heat pipes, or the frequency may be varied one or more times at steps as compaction occurs along the heat pipe as determined by the operator. If desired, the entire process may be automated since the frequency can be varied in response to the detection of the vibration amplitude without resorting to the human control of the apparatus.

Referring now to FIG. 4, the pipe pile 12 is illustrated as being grouted in place by the grouting material 13 and the heat pipes 20 and 21 are illustrated as being packed within the interior of the pipe pile 12 by the packed sand and water mixture 27 as discussed above with respect to FIG. 2. Although not illustrated, a protective casing can be used along the length of the hole between the grouting material 13 and the earth formation 11 as desired.

Thus it should be appreciated that there have been described herein the preferred embodiments of the present invention wherein various methods are described relating to the packing of one or more heat pipes within the interior of a pipe pile within an earth borehole. Although the preferred embodimentscontemplate the use of sand, the word sand is to be construed in a generic sense and it is contemplated that various sand-like materials or minerals can be used in place of the conventional silica sand. Furthermore, it should be appreciated that even though the preferred embodiments contemplate that the sand/water mixture be vibrated commencing with the addition of the sand to the water, those skilled in the art will recognize that a given amount of sand can be added to the water before commencing the vibration step. Likewise, after the vibration has ceased, dry sand can, if desired, be added to the very top of the interior of the pipe pile 12. Likewise, although the preferred embodiment contemplates that the heat pipes be placed within the interior of the pipe pile and then the water added to such interior, those skilled in the art will recognize that the water can be added to the interior of the pipe pile first and then the heat pipes placed within the pipe pile without departing from the spirit of the invention. Likewise, those skilled in the art will recognize that, on occasion, there may already be some amount of water within the interior of the pipe pile for various reasons and that a smaller amount of water, perhaps zero, need be added to the interior of the pipe pile before adding sand. Furthermore, the sand and water mixture can be vibrated by other means, for example, by vibrating the pipe pile itself or by inserting a vibrating rod into the sand and water mixture.

It should also be appreciated that while the preferred embodiment contemplates that the pipe pile is first grouted in place within an earth borehole in accordance with the principles of my aforementioned related United States patent application, both the grouting of the pipe pile within the earth borehole and the packing of the heat pipes within the interior of the pipe pile can be accomplished in a single step. Thus, by adding water to the annulus exterior to the pipe pile and also to the interior of the pipe pile having the heat pipes therein and shortly thereafter adding sand to the annulus exterior to the pipe pile and to the interior of the pipe pile while vibrating the pipe pile at an optimized frequency, the pipe pile is thus grouted within the earth borehole simultaneously with the packing of the heat pipes within the interior of the pipe pile.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method of packing at least one heat pipe within a pipe pile, comprising:

placing at least one heat pipe within the interior of said pipe pile;

metering a predetermined amount of water into the interior of said pipe pile;

placing sand in said water to form a sand and water mixture after said water is in place in the bottom of said pipe pile;

vibrating said sand and water mixture, said mixture having enough water to remain fluidized during said vibration; and

varying the frequency of said vibration to reinforce the amplitude of said vibration.

2. The method according to claim 1 wherein said at least one heat pipe comprises a pair of heat pipes.

3. A method of packing at least one heat pipe within a pipe pile, comprising:

placing at least one heat pipe within the interior of said pipe pile;

adding water to the interior of said pipe pile;

adding sand to said water to form a sand and water mixture within the interior of said pipe pile after said water is in place in the bottom of said pipe pile; vibrating said sand and water mixture, said mixture having enough water to remain fluidized during said vibration; and varying the frequency of said vibration to reinforce the amplitude of said vibration. 4. A method of packing at least one heat pipe within the interior of a pipe pile, comprising:

placing at least one heat pipe within the interior of a pipe pile; adding water to the interior of said pipe pile; adding sand to said water to form a sand and water mixture within the interior of said pipe pile after said water is in place in the bottom of said pipe pile; vibrating said sand and water mixture as said sand is added, said mixture having enough water to remain fluidized during said vibration; and varying the frequency of said vibration to reinforce the amplitude of said vibration. 5. A method of packing at least one heat pipe within the interior of a pipe pile, comprising:

placing at least one heat pipe within the interior of a pipe pile; adding water to the interior of said pipe pile; adding sand to said water to form a sand and water mixture within the interior of said pipe pile after said water is in place in the bottom of said pipe pile; vibrating said at least one heat pipe while said sand is being added to said water, said mixture having enough water to remain fluidized during said vibration; and varying the frequency of said vibration to reinforce the amplitude of said vibration. 6. A method of packing at least one heat pipe within the interior of a pipe pile, comprising:

placing a heat pipe within the interior of a pipe pile; adding water to the interior of said pipe pile; adding sand to said water to form a sand and water mixture within the interior of said pipe pile after said water is in place in the bottom of said pipe pile; V vibrating said sand and water mixture;

ceasing to vibrate said sand and water mixture while said mixture is still fluidized; and varying the frequency of said vibration to reinforce the amplitude of said vibration. 7. A method of packing at least one heat pipe within the interior of a pipe pile, comprising:

placing at least one heat pipe within the interior of a pipe pile; adding water to the interior of said pipe pile; adding sand to said water to form a sand and water mixture within the interior of said pipe pile after said water is in place in the bottom of said pipe pile;

the amplitude of said vibration. 

1. A method of packing at least one heat pipe within a pipe pile, comprising: placing at least one heat pipe within the interior of said pipe pile; metering a predetermined amount of water into the interior of said pipe pile; placing sand in said water to form a sand and water mixture after said water is in place in the bottom of said pipe pile; vibrating said sand and water mixture, said mixture having enough water to remain fluidized during said vibration; and varying the frequency of said vibration to reinforce the amplitude of said vibration.
 2. The method according to claim 1 wherein said at least one heat pipe comprises a pair of heat pipes.
 3. A method of packing at least one heat pipe within a pipe pile, comprising: placing at least one heat pipe within the interior of said pipe pile; adding water to the interior of said pipe pile; adding sand to said water to form a sand and water mixture within the interior of said pipe pile after said water is in place in the bottom of said pipe pile; vibrating said sand and water mixture, said mixture having enough water to remain fluidized during said vibration; and varying the frequency of said vibration to reinforce the amplitude of said vibration.
 4. A method of packing at least one heat pipe within the interior of a pipe pile, comprising: placing at least one heat pipe within the interior of a pipe pile; adding water to the interior of said pipe pile; adding sand to said water to form a sand and water mixture within the interior of said pipe pile after said water is in place in the bottom of said pipe pile; vibrating said sand and water mixture as said sand is added, said mixture having enough water to remain fluidized during said vibration; and varying the frequency of said vibration to reinforce the amplitude of said vibration.
 5. A method of packing at least one heat pipe within the interior of a pipe pile, comprising: placing at least one heat pipe within the interior of a pipe pile; adding water to the interior of said pipe pile; adding sand to said water to form a sand and water mixture within the interior of said pipe pile after said water is in place in the bottom of said pipe pile; vibrating said at least one heat pipe while said sand is being added to said water, said mixture having enough water to remain fluidized during said vibration; and varying the frequency of said vibration to reinforce the amplitude of said vibration.
 6. A method of packing at least one heat pipe within the interior of a pipe pile, comprising: placing a heat pipe within the interior of a pipe pile; adding water to the interior of said pipe pile; adding sand to said water to form a saNd and water mixture within the interior of said pipe pile after said water is in place in the bottom of said pipe pile; vibrating said sand and water mixture; ceasing to vibrate said sand and water mixture while said mixture is still fluidized; and varying the frequency of said vibration to reinforce the amplitude of said vibration.
 7. A method of packing at least one heat pipe within the interior of a pipe pile, comprising: placing at least one heat pipe within the interior of a pipe pile; adding water to the interior of said pipe pile; adding sand to said water to form a sand and water mixture within the interior of said pipe pile after said water is in place in the bottom of said pipe pile; vibrating said at least one heat pipe while said sand is being added to said water; ceasing to vibrate said at least one heat pipe short of adding sand in such an amount that said sand and water mixture would no longer be fluidized; and varying the frequency of said vibration to reinforce the amplitude of said vibration. 